Wellhead completion assembly capable of versatile arrangements

ABSTRACT

A wellhead completion assembly has a head connected to surface casing. A rotatable flange or the like can be used to connect various components to a threaded end of the head. A casing hanger installs in the head, and the hanger&#39;s upper end extends beyond the head&#39;s top edge. This exposed end has an external threaded connection to connect to various wellhead components using a rotatable flange or the like. For example, a locking ring can threadably connect to the head&#39;s threaded end to support the hanger in the head. Then, a rotatable flange can threadably connect to the hanger&#39;s exposed end so that another component, such as a completion spool or gate valve, can nippled up directly to the hanger. When the hanger is fluted, a pack-off assembly can allow testing off inner and outer sealing integrity via a test port accessible through an opening in the locking ring.

BACKGROUND

A well has one or more casings installed in a borehole to reinforce andseal it, and wellhead components install at the surface above theexposed end of the casings. For example, FIG. 1 shows a wellheadarrangement according to the prior art. Typically, an outermostconductor pipe is driven into place in the borehole, and a base assembly11 is on the exposed end of conductor pipe 10. A casing head 30 lands onthe base assembly 11 and connects to a surface casing 14 supportedinside the conductor pipe 10. Typically, the space between the casing 14and pipe 10 is filled with cement. One or more adapters 40 andcomponents 50 of a blow-out preventer can connect above the casing head30. As shown in FIG. 1, flanged connections are typically used toconnect the various components together.

Because various operations may be performed at the wellhead, thearrangement of components may be modified to accommodate differentoperations, pressures, and implementations. One typical wellheadoperation involves fracing. According to conventional practices, anisolation tool, such as a stinger, installs in the wellhead to isolatebores and outlets from pressures that may be higher thanpressure-ratings for the wellhead's flange connections.

In one typical wellhead arrangement, a casing hanger supports casing inthe casing head, and a tubing spool nipples to the casing head so thatanother hanger can be used in the tubing spool to support tubing in thecasing. Typically, an adapter must be installed on the casing head priorto nippling up the tubing spool so that the adapter can pack-off or sealaround the casing hanger. In another typical wellhead arrangement, afluted casing hanger support casing in the casing head so that drillingfluids during cementing operations are allowed to return through thehanger's flutes. Later, a pack-off bushing installs above the flutedcasing hanger to seal off the flutes. Typically, there is only a limitedability to test the seal created by such a pack-off.

SUMMARY

A wellhead completion assembly is capable of versatile arrangements. Theassembly has a first head component that connects to surface casing. Arotatable flange or the like can be used to connect various componentsto a threaded end of this first head component. Alternatively, secondhead components can threadably stack on top of one another and canthreadably stack on top of the first head component to create amulti-bowl arrangement.

For either arrangement, the assembly can use a casing hanger thatinstalls in the head (i.e., first head component in a single-bowlarrangement or the top most second head component in a multi-bowlarrangement). In either case, the hanger's upper end extends beyond thehead's top edge. This exposed end has an external threaded connection toconnect to various wellhead components using a rotatable flange or thelike. For example, a locking ring can threadably connect to the head'sthreaded end to support the casing hanger in the head. Then, a rotatableflange can threadably connect to the hanger's exposed end so thatanother component, such as a completion spool or gate valve, can nippledup directly to the casing hanger.

The casing hanger can be fluted or not, and a pack-off plate can be usedto seal the casing hanger in the head. This pack-off plate can have atest port accessible through an opening in the locking ring holding thehanger in the head. The test port allows operators to test the inner andouter sealing integrity of the pack-off plate. In one particulararrangement, the casing hanger has a sealing ring positioned about itsexternal surface. The pack-off plate threads onto an external threadedconnection on the casing hanger, and a lip on the pack-off platepositions in wedged engagement between the sealing ring and a portion ofthe external surface of the casing hanger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view illustrating a wellheadarrangement according to the prior art.

FIG. 2 is a cross-sectional view illustrating a wellhead completionassembly in one arrangement having portion of a Blow-Out Preventer (BOP)stack nippled up to a casing head.

FIG. 3A is a cross-sectional view illustrating the assembly of FIG. 2 inanother arrangement having a completion spool nippled up to the casinghanger.

FIG. 3B is a detail illustrating portions of the casing hanger, thelocking ring, and the casing head of FIG. 3A.

FIG. 4 is a cross-sectional view illustrating the assembly of FIG. 2 inyet another arrangement having a gate valve nippled up to the casinghanger.

FIGS. 5A-5B are top and cross-sectional views illustrating a flutedcasing hanger for the disclosed assembly.

FIG. 6 is a cross-sectional view illustrating a pack-off plate.

FIG. 7A is a partial cross-sectional view illustrating a flange and thepack-off components on the fluted casing hanger of FIGS. 5A-5B.

FIG. 7B is a detail of FIG. 7A illustrating features of the pack-offcomponents.

FIG. 8 is a cross-sectional view illustrating the casing head of FIG. 2landed through a riser.

FIGS. 9A-9B are cross-sectional views illustrating the casing head ofFIG. 2 used with other wellhead components.

FIG. 10A is a cross-sectional view illustrating another embodiment of awellhead completion assembly in one arrangement.

FIG. 10B is a cross-sectional view illustrating the assembly of FIG. 10Ain another arrangement.

FIGS. 11A-11DE are cross-sectional views illustrating a wellheadcompletion assembly having modular head components in various stages ofassembly.

FIGS. 12A-12B are cross-sectional views illustrating the modularassembly using only a first head component.

FIG. 13 is a cross-sectional view illustrating the modular assemblyusing three head components.

FIGS. 14A-14C are cross-sectional views illustrating the modularassembly when stuck pipe occurs.

FIGS. 15A-15C are cross-sectional views illustrating the modularassembly having a control line when stuck pipe occurs.

DETAILED DESCRIPTION

A versatile wellhead completion assembly is capable of variousarrangements. The assembly includes a casing head that lands on aconductor pipe and connects to surface casing. The head's upper end hasan external threaded connection to which various components can beconnected depending on the desired arrangement. For example, a rotatableflange or other connector can thread onto the head's upper end, and acomponent of a blow-out preventer (BOP) can bolt to the rotatable flangeabove the casing head.

The assembly also includes a casing hanger that lands in the casing headto support production casing within the surface casing. When installedin the head, the hanger's upper end extends beyond the head's top edge.This exposed end has an external threaded connection that allows variouscomponents to connect to the hanger's upper end depending on the desiredarrangement. For example, a locking ring can threadably connect to thehead's external threaded connection to support the casing hanger in thecasing head. Then, a rotatable flange or other connector can threadablyconnect to the hanger's exposed end so that a completion spool, gatevalve, or other wellhead component can bolt to the rotatable flangeabove the casing hanger.

In other arrangements, the casing head can be used with conventionalwellhead components and can be landed through a riser using a runningtool threaded to internal threads in the casing head. In addition, thecasing hanger used in the various arrangements can be fluted, and apack-off assembly that allows testing a inner and outer seals can beused with the fluted casing hanger. In still other arrangements, modularhead components of the assembly permit operators to make variousarrangements of the head components to suit their needs in eithersingle-bowl or multiple-bowl arrangements and to facilitate contingencyoperations in the event a stuck pipe occurs.

Turning now to the drawings, FIG. 2 illustrates a well completionassembly having a casing head 100 and a casing hanger 200. The casinghead 100 with a landing ring 22 attached thereto lands on a support ring20 on an exposed end of conductor pipe 10, and an internal threadedconnection 104 connects to surface casing 12. Side ports 102 for valvesor the like are provided in the head's bore 101 for various uses duringwell operations. When the casing head 100 is installed as shown, flutes(not shown) in the rings 20/22 can allow cement to be inserted betweenthe conductor pipe 10 and the surface casing 12 during a cementing job.

In the arrangement, a rotatable flange 110 threadably connects to anexternal threaded connection 106 on the casing head's upper end 103a,and a BOP stack component 50 nipples up to the casing head 100 bybolting to the flange 110. To seal this connection, a gasket is disposedin a groove at head's top edge. Rather than using the rotatable flange110 as shown, a drilling adapter, such as element 530 shown in FIG. 10A,or other connector could alternatively be used.

Also in the arrangement, the casing hanger 200 has production casing 14connected by an internal threaded connection 204 at the hanger's lowerend 203b. To install the hanger 200 and the casing 14, a running tool 52connects by a coupling 54 to an external threaded connection 206 at thehanger's upper end 203a, and the hanger 200 and the casing 14 are runthrough the BOP stack component 50 and into the casing head 100. Oncerun in, the casing hanger 200 lands in the head 10 by engaging aninternal shoulder 103 so that the production casing 14 is supportedwithin the surface casing 12.

As will be appreciated, each of the components of the assembly iscomposed of a suitable material known in the art for a wellheadcomponent. Preferably, the threaded connections (106, 204, and 206) haveACME-2G left-handed thread forms. For some exemplary dimensions, theconductor pipe 10 may be 16-in. casing, and the surface and productioncasings 12/14 may respectively be 9⅝-in. and 4½-in. casings. Theconnection of the rotatable flange 110 to the BOP stack component 50 maybe 11-in. rated at a working pressure of 5,000-PSI. As one skilled inthe art will appreciate, these values are provided as examples forillustrative purposes, and components of the assembly can be sized for13-inch connections and other sizes of casing.

During operations, it would be desirable to be able to nipple up atubing spool above a production casing hanger without requiring the useof secondary pack-off to seal around the hanger. As shown in FIG. 3A,the disclosed assembly allows a completion spool 60 to nipple up to thecasing hanger 200 of the disclosed assembly without the need forsecondary pack-off. In this arrangement, a locking ring or head ring 120defining a central opening 122 installs over the hanger's end 203aexposed above the head 100, and internal threads on the ring's sides 126couple to the external threaded connection 106 on the casing head 100.This connection 106 can be 11-in. rated at a working pressure of10,000-PSI. As shown in the detail of FIG. 3B, the ring's inside surface124 engages the hanger's upper shoulder 207 to hold the hanger 100 inthe head 100. Also, the inside surface 122 engages a gasket 108 disposedin a groove at the head's top edge.

With the ring 120 installed, the tubing spool 60 call couple directly tothe exposed end 203a of the hanger 200. In particular, a rotatableflange 62 or other connector threads onto the hanger's external threadedconnection 206, and the spool 60 bolts to the rotatable flange 62. Agasket is disposed in a groove at the hanger's top edge to seal theconnection. This connection between hanger 200 and spool 60 can be 41/16-in. rated at a working pressure of 10,000-PSI, for example. Withthe spool 60 connected, other components can then be connected above thespool 60, and tubing (not shown) can eventually be hung in the spool'sbowl using a tubing hanger (not shown). Because the completion spool 60nipples up directly to the hanger 200, the casing hanger 200 essentiallyacts as a spool, and the need for secondary pack-off is eliminated.

As shown in detail in FIG. 3B, the hanger's upper shoulder 207 defines atest port 208 that communicates between two sealing seats 209 disposedabout the hanger's outer cylindrical surface. With the hanger 200installed in the head's internal bore 101 as shown, this test port 208is accessible through the ring's opening 122 so that the seal formedbetween the sealing seats 209 and the casing head's internal bore 101can be tested.

FIG. 4 shows a similar arrangement with a gate valve 65 nipple up to thecasing hanger 200 of the assembly. Again, the rotatable flange 62couples to the external threaded connection 206 on the exposed end 203aof the hanger 200, and the gate valve 65 bolts to the flange 62. As willbe appreciated, the gate valve 65 may be used for facing operations orthe like. With respect to frac operations, it would be desirable to beable to frac at high pressures without needing to use an isolation toolin the wellhead. In current arrangement of the disclosed assembly, thereis no need to use an isolation tool (or a nipple up/down apparatus forsuch an operation). Rather, interior frac pressures can reach as high asthe internal yield pressure of the production casing 14 itself becausethe housing of the casing 14 communicates directly with the gate valve65 through the casing hanger 200. Therefore, frac pressures that can beused with the disclosed assembly are not limited by conventional flangepressure ratings of adapters or the like that would typically be usedabove a production casing hanger.

The hanger 200 shown in FIG. 4 has flutes that allow fluid returns pastthe hanger 200 when used in some arrangements. In FIG. 4, however, apack-off assembly 210 having a pack-off plate and other components formsa seal between the fluted hanger 200 and the inside surface of lockingring or head ring 120. When this form of pack-off is done, it isdesirable to have an adequate and convenient way to test the pack-off'sinner and outer seals. In the prior art, however, the only way to testthe integrity of a pack-off's seals requires operators to nipple up thenext spool above the pack-off assembly and to then perform a flangepressure test. For example, FIG. 9A discussed below shows a conventionalpack-off plate 74 having an inner seal that engages casing 14 and havingan outer seal that engages casing head 100. To test the seals, a tubingspool 70 must be rippled up to the casing head 100, and a flangepressure test must be performed using a test port 73 on the spool 70. Ifthe test fails, operators have to nipple down the spool 70 and pull outthe pack-off plate 74 to investigate the cause. This procedure can betime intensive.

In contrast, the pack-off assembly 210 in FIG. 4 has a top-access testport 212 accessible through the sealing ring's opening 122. This testport 212 communicates between two sets of inner and outer seals on theassembly 210. In this way, the sealing integrity of the assembly's innerand outer seals can be tested simultaneously and as soon as the assembly210 is installed so that time can be saved on site. Further details of afluted hanger and a pack-off assembly are discussed below with referenceto FIGS. 5A through 8C.

FIGS. 5A-5B illustrate a fluted casing hanger 300 for use with thedisclosed assembly in top and cross-sectional views, respectively. Aswith other hangers disclosed herein, the fluted hanger 300 has aninternal bore 302 with an internal threaded connection 303 at its lowerend 303b to connect to production casing (not shown). In addition, thehanger's upper end 303a has an external threaded connection 306 forcoupling to running tool as in FIG. 2 or to a rotatable flange as inFIG. 3A. Furthermore, the hanger's top edge defines an annular well 308for a gasket (not shown) used to seal engagement between the hanger 300and the various other components discussed herein.

Being fluted, however, the hanger's lower end 303b defines a pluralityof flutes or cutaways 304 (four shown in FIG. 5A) that enable fluidreturns to communicate past the hanger 300. In another distinction, thehanger 300 as shown in FIG. 5B has a blunt or flat lower end 305 asopposed to the substantially extended and narrowed lower end (e.g., 214:FIG. 4) of the other hangers disclosed herein. It will be appreciatedthat any of the other hangers (either fluted or not) disclosed hereinmay have a similar blunt end 305 if desired.

As briefly discussed above in FIG. 4, a pack-off assembly 210 can beused to seal communication through flutes of a fluted hanger whenreturns are no longer desired. When used, the pack-off assembly 210preferably allows the sealing integrity of inner and outer seals to betested in an adequate and convenient way. For such as a pack-offassembly, FIG. 6 illustrates a pack-off plate or sealing ring 400capable of such testing ability, and FIGS. 7A-7B illustrate the pack-offplate 400 and an additional sealing ring or hanger ring 430 positionedon the fluted casing hanger 300 of FIGS. 5A-5B.

As best shown in FIGS. 7A-7B, the sealing ring or hanger ring 430positions adjacent a lowermost shoulder 309a on the hanger 300. Thepack-off plate 400 (shown in cross-section in FIG. 6) has a centralopening 402 and positions over the hanger's narrower end 303a andthreads its internal threads 407 onto intermediate threaded connection307 on the hanger 300. This pack-off plate 400 may be referred to as aproduction casing hanger pack-off or an H-plate.

As the pack-off plate 400 is tightened onto the hanger 300, internalseals 450 (e.g., O-rings) on the pack-off plate 400 eventually engage aside portion 309b of the hanger's surface, while outer seals 440 (e.g.,O-rings) engage the internal wall of the casing head's bore (not shown).Likewise, the plate's lower lip 404 wedges in between the lowermost ring430 and a side portion 309b of the hanger's surface so that thelower-most ring 430 seals against the internal wall of the casing head'sbore (not shown).

To test the sealing integrity, the pack-off plate 400 defines a testport 406 in its top surface 405 that is accessible when the locking ring(e.g., 120 in FIG. 4) is used. As best shown in the cross-section of theplate 400 in FIG. 6, the test port 406 communicates with spaces betweenthe outer and inner seats 408/409 for the seals (440/450) so that theirsealing integrity can be tested. Because this test port 406 isaccessible through the locking ring's opening (122), this testing can bedone during partial assembly of the pack-off or after complete assemblyof the arrangement.

In addition to being used with the casing hanger 200, pack-off assembly210, and other components discussed above, the casing head 100 can beused on its own with various other wellhead components in a number ofother arrangements. In one example shown in FIG. 8, the casing head 100can be run through a riser 16 and landed on a support ring 20 using aninternal running tool 18. To run the head 100, the internal running tool18 has a coupling 19 that attaches to an internal threaded connection107 in the casing head's bore 101.

In other uses, the casing head 100 can also be used on its own inconjunction with some conventional wellhead components. For example,FIG. 9A shows the casing head 110 having a completion spool 70 nippledup to the head 100 with a rotatable flange 110. FIG. 9B shows a similararrangement, but in this example, a completion spool 80 and adapter 82nipple up to the casing head 100 with a rotatable flange 110.

In both arrangements, a conventional hanger 76 having slips 77 lands onthe head's internal shoulder 103 to support the production casing 14,and a conventional pack-off plate 74 seals against the production casing14 and the head 100. Segmented rings 72 engage against the productioncasing 14 within the spool 70 in FIG. 9A, while internal seals in theadapter 82 engage against the end of production casing 14 in FIG. 9B.

The casing head 100 disclosed above represents a single-bowl type,meaning that it defines a single bowl and has a length for supporting asingle hanger. FIGS. 10A-10B illustrates a wellhead completion assemblyhaving a casing head 500 that represents a double-bowl type.Accordingly, one casing hanger 510 (FIG. 10A) or two casing hangers510/540 (FIG. 10B) can be used with this casing head 500. Although shownas fluted, the casing hangers 510/540 could be mandrel hangers, ifdesired.

In the arrangement of FIG. 10A, a BOP stack component 50 nipples up tothe casing head 500. In this example, the connection uses a drillingadapter 530 that has a locking assembly 532 for quick connect to thecasing head 500, pack-off screws 534 for other purposes, and a flange536 for bolting to the BOP stack component 50. The casing hanger 510lands in the casing head 500 through the BOP stack component 50 using arunning tool (not shown). A pack off assembly 520 having pack-offelements 522 installs above the casing hanger 510, and pack-off screws524 on the head 500 engage the elements 522. Once installed, thepack-off assembly 520 forms an additional bowl in the head 500. In thisexample, the conductor pipe 10 can be 20-in. casing, and the surfacecasing 12 can be 9⅝-in casing. The casing hanger 510 can support 7-in.production casing.

In the arrangement of FIG. 10B, the casing hanger 510 and the pack-offassembly 520 again install in the casing head 500 toward its lower end503b, and a fluted hanger 540 with flutes on its lower end 543b and apack off assembly 545 install in the upper end 503a of the casing head500. A locking ring 550 threads onto the upper end 503a of the casinghead 500 and engages the pack-off assembly 545, and a completion spool560, gate valve, or other component nipples up to the upper end 543a ofthe fluted hanger 540 with a rotatable flange 562 or other connector. Inthis example, the first hanger 510 can support 7-in. production casing14, while the second hanger 540 can support 4.5-in. casing 15.

In addition to these arrangements of FIGS. 10A-10B, the double-bowl typecasing head 500 can be landed through a 20-in. riser using a runningtool in much the same manner as depicted in the example of FIG. 8, withthe exception that the running tool couples to the outer threadedconnection at the top or upper end 503a of the casing head 500.Moreover, the casing head 500 and other components of FIGS. 10A-10B canbe used with completion spools, adapters, and other conventionalcomponents similar to the arrangements in FIGS. 9A-9B (e.g., elements70, 72, 74, 76, 77, 80, and 82).

The double-bowl type casing head as shown in FIGS. 10A-10B can be usedin various operations when several casing strings are to be rundownhole. FIGS. 11A-11D illustrate another wellhead completion assembly600 in various stages of assembly that can support several casingstrings. In addition, to being able to support multiple strings, thisassembly 600 has modular head components 610 and 620 that offer a numberof advantages, including allowing the assembly 600 to be assembled indifferent arrangements and facilitating contingency operations when astuck pipe occurs before a hanger can be properly landed in the head.

As shown in FIG. 11A, the modular assembly 600 includes first and secondhead components 610 and 620. The first head component 610 can be similarto the casing head of previous embodiments, such as casing head 100 inFIG. 2, and can be used alone in a single bowl type of arrangement.Alternatively, the second head component 620 can connect to the firsthead component to make a double-bowl type of casing head.

In assembling the double bowl arrangement, for example, the first headcomponent 610 connected to outer casing 12 lands on the landing assembly20, and the second head component 620 supported by running tool 54threads to the first component 610 at a threaded connection 630. Thisthreaded connection 630 can use the same type of threading and rating asprevious embodiments. For example, this connection 630 can be similar tothe connection 106 in FIG. 2 having ACME-2G left-handed thread form andcan be 11-in. rated at a working pressure of 10,000-PSI. Holes 632 andsetscrews (not shown) may also be used to couple the second component620 to the first component 610.

As shown in FIG. 11B, another running tool 54 runs a hanger 650 andattached inner casing 14 through the head components 610/620 and landsthe hanger 650 on the shoulder 612 inside the first component 610.Subsequently, as shown in FIG. 11C, another running tool 56 lands apack-off plate 660 above the hanger 650. The modular assembly 600'sresulting double-bowl type of arrangement is shown in FIG. 11D. At thispoint in the assembly as shown in FIG. 11E, additional pack-offcomponents 522, another inner casing 15, and an additional hanger 540can be landed in the second head component 620 and a head ring 550 canbe used, as with the assembly in FIGS. 10A-10B. In this way, the modularassembly 600 can support multiple casing strings (e.g., 14, 15). Forexample, an 11-inch embodiment of the assembly 600 could support twocasing strings, while a 13-inch embodiment of the assembly 600 couldsupport three casing strings.

As shown in FIGS. 11A-11D, the first and second head components 610/620of the modular assembly 600 can be used to create a double-bowl type ofcasing head. Because the disclosed assembly 600 is modular, the firsthead component 610 can be used by itself. As shown in FIGS. 12A-12B, forexample, the first head component 610 can be landed on the landingassembly 20 with a running tool 54, and a quick connect drilling adapter530 or some other desired component can be attached to the firstcomponent 610 to complete the assembly. Alternatively, the first headcomponent 610 can be used in other arrangements disclosed herein, suchas in FIGS. 2, 3A, 4, and 9A-9B. In another alternative shown in FIG.13, two of the second head components 620a-b can be stacked on top ofone another above the first head component 610 to create a threecomponent modular assembly, which can be used to support multiple casingstrings.

Not only does the modular assembly 600 provide for versatilearrangements, but it facilitates contingency operations when a stuckpipe occurs. When running the casing 14 and hanger 650 through the headcomponents 610/620 and the outer casing 12, for example, the innercasing 14 may become stuck in what is commonly referred to as a stuckpipe situation—an example of which is shown in FIG. 14A. Because theinner casing 14 cannot be inserted enough to allow the attached hanger650 to be landed on the shoulder 612, operators must perform acontingency operation that involves using slips to secure the innercasing 14 in tension within the casing head and cutting the excessportion from the inner casing 14 that has been prevented from passingthrough the casing head.

In a conventional double-bowl casing head, cutting the excess casing canbe difficult because the point at which the cut must be made lies deepwithin the double-bowl casing head. In other words, an operator has tocarefully cut the casing within the confined space of the double-bowlhead with a welding tool and then to prepare the end of the cut casingproperly for further operations.

The modular assembly 600, however, facilitates stuck pipe contingencyoperations. When a stuck pipe occurs as in FIG. 14A, operators positiona slip assembly 670 and pack-off 672 in the first component 610 as shownin FIG. 14B and then remove the second component 620 from the firstcomponent 610 at the threaded connection 630. Removing the secondcomponent 620 leaves the excess casing 14 exposed above the firstcomponent 610. Operators can then more readily cut the excess casing 14at the appropriate point, level the cut end 15, and create the neededchamfer at the edge. After these steps have been completed, operatorscan reconnect the second component 620 to the first component 610.Alternatively, operators can attach a rotating flange 674 to theconnection end 631 of the first component 610 as shown in FIG. 14C orcouple components of some other desired arrangement to the firstcomponent 610.

In addition to facilitating preparation of the inner casing 14 duringstuck pipe contingency operations, the modular assembly 600 also helpsoperators perform modifications to a control line when a stuck pipeoccurs. For example, FIG. 15A shows the modular assembly 600 having acontrol line 700 that runs down the annulus to a valve or the like (notshown). The control line 700 connects by a ferrule coupling 702 to ahanger 650, and a side coupling 704 in the first head component 610communicates with a port in the hanger 650 to communicate with thecontrol line 700.

If a stuck pipe occurs while running the inner casing 14, the hanger650, and the control line 700 downhole, operators have to modify thearrangement of the control line 700 to connect it to the side coupling704. In a conventional double-bowl type of head, operators would have tomodify the control line's connection by making modifications deep withinthe double-bowl head and confined in the annulus between the innercasing and the head.

The disclosed modular assembly 600, however, alleviates some of thisdifficulty. For example, as shown in FIG. 15B, the second component 620can be removed from the first head component 610 giving operators easieraccess to the control line 700 and the inside of the coupling 704.Before putting the slip assembly 670 and pack-off 672 in the head, forexample, operators can wind excess amounts of control line 700 in wraps705 around the casing 14 and attach the line 700 to the coupling 704inside the first component 610 while having easier access inside theannulus. After setting up the control line 700, putting the slipassembly 670 and pack-off 672 in the first head component 610, andcutting the excess of the casing 14, operators can reconnect the secondcomponent 620 to the first component 610. Alternatively, operators canattach a rotating flange 674 to the end 630 of the first component 610as shown in FIG. 15C, or couple components of some other desiredarrangement to the first component 610.

The foregoing description of preferred and other embodiments is notintended to limit or restrict the scope or applicability of theinventive concepts conceived of by the Applicants. For example, it willbe appreciated with the benefit of the present disclosure thatcomponents of one embodiment of the wellhead completion assembly can becombined with components of another embodiment to produce a variety ofversatile arrangements for well completions. In exchange for disclosingthe inventive concepts contained herein, the Applicants desire allpatent rights afforded by the appended claims. Therefore, it is intendedthat the appended claims include all modifications and alterations tothe full extent that they come within the scope of the following claimsor the equivalents thereof.

What is claimed is:
 1. wellhead completion assembly, comprising: acasing head connecting to casing at a wellhead and having a firstexternal threaded connection adjacent a first end; a casing hangerlanding in the casing head and having a shoulder and a second end, thesecond end extending beyond the first end of the casing head and havinga second external threaded connection, the second external threadedconnection connectable to a connector to support at least one additionalcomponent above the casing hanger; a pack-off plate disposed on thesecond end of the casing hanger adjacent the shoulder, the pack-offplate having an upper surface, an inner portion, and an outer portion,the inner portion sealable sealably engaging an external surface of thecasing hanger, the outer portion sealable sealably engaging an internalsurface of the casing head; and a head ring threadably connecting to thefirst external threaded connection of the casing head and defining anopening through which the second end of the casing hanger extends, aportion of the head ring directly engaging the upper surface of thepack-off plate.
 2. The assembly of claim 1, wherein the pack-off platecomprises: a first pair of sealing seats on the outer portion, a secondpair of sealing seats on the inner portion, and a test port defined inthe upper surface and accessible through the opening in the head ring,the test port communicating with the inner and outer portions betweenthe first and second pairs of sealing seats.
 3. The assembly of claim 1,wherein the casing head comprises a single-bowl arrangement defining aninternal shoulder within an internal bore, the casing hanger landing onthe internal shoulder to be supported therein.
 4. The assembly of claim1, wherein the casing head comprises a double-bowl arrangement definingan internal shoulder within an internal bore, the casing hanger landingon one or more components supported by the internal shoulder.
 5. Theassembly of claim 1, wherein the casing hanger defines at least oneflute, and wherein the pack-off plates plate seals fluid communicationthrough the at least one flute.
 6. The assembly of claim 1, furthercomprising a hanger ring positionable about the external surface of thecasing hanger, and wherein the pack-off plate comprise a lippositionable in wedged engagement between the hanger ring and a portionof the external surface of the casing hanger.
 7. The assembly of claim4, wherein the casing head for the double-bowl arrangement comprises atleast two head components interconnectable to one another, a first ofthe head components having the internal shoulder therein, a second ofthe head components having the first external threaded connection towhich the head ring threadably connects.
 8. The assembly of claim 6,wherein the inner portion of the pack-off plate threadably connects to athird threaded connection on the external surface of the casing hanger.9. A wellhead completion assembly, comprising: a casing head connectingto a first casing and having a first external threaded connectionadjacent a first end, the casing head comprising a double-bowlarrangement defining an internal shoulder within an internal bore; acasing hanger landing on one or more other components supported by theinternal shoulder of the casing head, the casing hanger defining atleast one flute and having a shoulder and a second end, the second endextending beyond the first end of the casing head and having a secondexternal threaded connection, the second external threaded connectionconnectable to a connector to support at least one additional componentabove the casing hanger; a head ring threadably connecting to the firstexternal threaded connection of the casing head and defining an openingthrough which the second end of the casing hanger extends; and at leastone pack-off component positioning positioned between the shoulder ofthe casing hanger and a portion of the head ring, the at least onepack-off component sealably engaging an external surface of the casinghanger and sealably engaging an internal surface of the casing head, theat least one pack-off component sealing fluid communication through theat least one flute in the casing hanger.
 10. The assembly of claim 9,wherein the casing head for the double-bowl arrangement comprises atleast two head components interconnectable to one another, a first ofthe head components having the internal shoulder therein, a second ofthe head components having the first external threaded connection towhich the head ring threadably connects.
 11. The assembly of claim 9,wherein the at least one pack-off component comprises a pack-off platehaving— an inner portion threadably connecting to a third threadedconnection on the external surface of the casing hanger, and an outerportion sealably engaging the internal surface of the casing head. 12.The assembly of claim 11, wherein the at least one pack-off componentcomprises a hanger ring positionable about the external surface of thecasing hanger, and wherein the pack-off plate comprise a lippositionable in wedged engagement between the hanger ring and a portionof the external surface of the casing hanger.
 13. The assembly of claim9, wherein the at least one pack-off component comprises a pack-offplate having— a first pair of sealing seats on an outer portion, asecond pair of seals sealing seats on an inner portion, and a test portdefined in an upper surface of the plate and accessible through theopening in the head ring, the test port communicating with the outerportion between the first pair of sealing seats and communicating withthe inner portion between the second pair of sealing seats.
 14. A systemfor a wellhead completion assembly, comprising: a first head componenthaving one end connectable to casing at a wellhead and having a firstexternal threaded connection adjacent another end; and second headcomponents each having second an internal threaded connectionsconnection adjacent one end and having a second external threadedconnections connection adjacent another end, the second each internalthreaded connection connectable to the first external threadedconnection on the first head component, the second internal and externalthreaded connections of each of the second head components beingcomplementary and threadably interconnectable to one another, whereinthe first head component is Used independently on the wellhead for asingle-bowl arrangement of the wellhead completion assembly, wherein oneof the second head components is used in conjunction with the first headcomponent for a first multiple-bowl arrangement of the wellheadcompletion assembly, the second internal threaded connection of the onesecond head component connecting to the first external threadedconnection on the first head component to stack the one second headcomponent on top of the first head component; and wherein two or more ofthe second head components are used in conjunction with the first headcomponent for second multiple-bowl arrangements of the wellheadcompletion assembly, the second internal and external threadedconnections of the second head components interconnecting to one anotherto stack the two or more second head components on top of one another,the internal threaded connection of a lowermost one of the second headcomponents connecting to the first external threaded connection on thefirst head component to stack the second head components on top of thefirst head component.
 15. The system for the assembly of claim 14,further comprising: a casing hanger supported supportable in thewellhead completion assembly, the casing hanger having a distal endextending beyond the first head component in the single-bowl arrangementor beyond a topmost end one of the second head components in themultiple-bowl arrangements of the wellhead completion assembly, thedistal end having an external threaded connection connectable to aconnector to support at least one additional component above the casinghanger; and a head ring threadably connectable to the first externalthreaded connection on the first head component in the single-bowlarrangement or threadably connectable to the second external connectionof a topmost one of the second head components in the multi-bowlarrangement multiple-bowl arrangements, the head ring defining anopening through which the distal end of the casing hanger extends. 16.The system for the assembly of claim 15, wherein a portion of the headring directly engages a shoulder of the casing hanger, and wherein thecasing hanger comprises— a pair of sealing seats on an outer surface,and a test port defined in the shoulder and accessible through theopening in the head ring, the test port communicating between the pairof sealing seats.
 17. The system for the assembly of claim 15, furthercomprising a pack-off plate disposed in the topmost end one of thewellhead completion assembly head components between the casing hangerand a portion of the head ring, wherein the pack-off plate comprises: anupper surface positioning adjacent the portion of the head ring; aninner portion engaging an external surface of the casing hanger, and anouter portion engaging an internal surface of the wellhead completionassembly.
 18. The system for the assembly of claim 17, wherein thepack-off plate comprises: a first pair of sealing seats on the outerportion, a second pair of sealing seats on the inner portion, and a testport defined in the upper surface and accessible through the opening inthe head ring, the test port communicating with the inner and outerportions between the first and second pairs of sealing seats.
 19. Thesystem for the assembly of claim 14, further comprising: a hub threadingon the first external threaded connection of the first head component inthe single-bowl arrangement or threading on the second external threadedconnection of the topmost one of the second head components in themulti-bowl multiple-bowl arrangements; and an adapter disposing disposedon the an end of one the first or second head component components andlocking to the hub, the adapter connecting connectable to at least oneadditional component above the wellhead assembly.
 20. The system for theassembly of claim 14, wherein in the first and second multiple-bowlarrangements, the one or more second head components are removable fromthe first head component to expose an end of a stuck pipe in thewellhead completion assembly; and wherein a rotatable flange connects tothe first external threaded connections of the first head component tosupport one or more additional components above the first headcomponent.
 21. A hanger pack-off assembly, comprising: a casing hangerpositionable in a casing head and having a first external threadedconnection about an external surface; a hanger ring positionable aboutthe external surface of the casing hanger; and a pack-off plate definingan a first opening through first and second sides of the plate, thefirst opening having a first internal threaded connection threading ontothe first external threaded connection on the casing hanger, an outersurface of the plate having a first pair of sealing seats formedthereabout, an inner surface of the plate having a second pair ofsealing seats formed thereabout, a test port defined in the first sideof the plate and communicating with the inner and outer surfaces betweenthe first and second pairs of sealing seats, the pack-off platecomprising a lip positionable in wedged engagement between the hangerring and a portion of the external surface of the casing hanger.
 22. Theassembly of claim 21, further comprising a head ring threadablyconnecting connectable to the casing head and defining an a secondopening therethrough, wherein the casing hanger has a distal endextending through the second opening, the distal end having a secondexternal threaded connection to which a component connects to the casinghanger.
 23. A wellhead completion method, comprising: connecting acasing head to surface casing; landing a casing hanger in the casinghead to support production casing in the surface casing such that anupper end of the casing hanger extends beyond an upper end of the casinghead; disposing a pack-off plate on the upper end of the casing hanger,the pack-off plate sealably engaging an external surface of the casinghanger and sealably engaging an internal surface of the casing head;threadably connecting a head ring on the upper end of the casing headand directly engaging an upper surface of the pack-off plate with thehead ring, the upper end of the casing head fitting through an openingof the head ring; threading a connector to the upper end of the casinghanger; and connecting an additional component above the casing hangerby connecting to the connector.
 24. The method of claim 23, whereindisposing the pack-off plate on the upper end of the casing hangercomprises threading an inside portion of the pack-off plate on externalthread threads on the upper end of the casing hanger.
 25. The method ofclaim 23, wherein disposing the pack-off plate on the upper end of thecasing hanger comprises sealing an inner pair of seals on the pack-offplate against the external surface of the casing hanger and sealing anouter pair of seals on the pack-off plate against the internal surfaceof the casing head.
 26. The method of claim 25, further comprisingtesting the inner and outer pairs of seals via a test port defined inthe upper surface of the pack-off plate and accessible through theopening in the head ring.
 27. The method of claim 23, wherein disposingthe pack-off plate on the upper end of the casing hanger comprises:wedging a lip on the pack-off plate between a hanger ring and theexternal surface of the casing hanger, and engaging the hanger ringagainst the internal surface of the casing head.
 28. The method of claim23, wherein threading the connector to the upper end of the casinghanger comprises threading a rotatable flange to the upper end of thecasing hanger.
 29. The method of claim 28, wherein connecting theadditional component above the casing hanger comprises connecting a gatevalve for a facing operation to the rotatable flange.
 30. The method ofclaim 23, wherein before threadably connecting the head ring, threadingthe connector to the upper end of the casing hanger, and connecting theadditional component above the casing hanger, the method comprisesinitially removing a blow out preventer stack and a first rotatableflange from the casing head, the first rotatable flange being threadedon an external thread on the casing head.
 31. The method of claim 30,wherein the first rotatable flange is rated for a first workingpressure, and wherein the connector threading to the upper end of thecasing hanger comprises a second rotatable flange having a secondworking pressure greater than the first working pressure.
 32. The methodof claim 23, wherein landing the casing hanger comprises passing thecasing hanger on a running tool through a blow out preventer stackinstalled on the casing head.
 33. A wellhead completion assembly,comprising: a casing head connecting to casing at a wellhead and havinga first external threaded connection adjacent a first end; a casinghanger landing in the casing head and having a second end and ashoulder, the casing hanger comprising a pair of sealing seats on anouter surface and comprising a test port defined in the shoulder, thetest port communicating between the pair of sealing seats, the secondend extending beyond the first end of the casing head and having asecond external threaded connection, the second external threadedconnection connectable to a connector to support at least one additionalcomponent above the casing hanger; and a head ring threadably connectingto the first external threaded connection of the casing head anddefining an opening through which the second end of the casing hangerextends, a portion of the head ring directly engaging the shoulder onthe casing hanger, the test port in the shoulder of the casing hangerbeing accessible through the opening in the head ring.
 34. The assemblyof claim 33, wherein the casing head comprises a single-bowl arrangementdefining an internal shoulder within an internal bore, the casing hangerlanding on the internal shoulder to be supported therein.
 35. Theassembly of claim 33, wherein the casing head comprises a double-bowlarrangement defining an internal shoulder within an internal bore, thecasing hanger landing on one or more components supported by theinternal shoulder.
 36. The assembly of claim 35, wherein the casing headfor the double-bowl arrangement comprises and at least two headcomponents interconnectable to one another, a first of the headcomponents having the internal shoulder therein, a second of the headcomponents having the first external threaded connection to which thehead ring threadably connects.
 37. A wellhead completion assembly,comprising: a casing head connecting to a first casing and having afirst external threaded connection adjacent a first end, the casing headcomprising a double-bowl arrangement defining an internal shoulderwithin an internal bore; a casing hanger landing on one or more othercomponents supported by the internal shoulder of the casing head, thecasing hanger having a shoulder and a second end, the second endextending beyond the first end of the casing head and having a secondexternal threaded connection, the second external threaded connectionconnectable to a connector to support at least one additional componentabove the casing hanger; a head ring threadably connecting to the firstexternal threaded connection of the casing head and defining an openingthrough which the second end of the casing hanger extends; a hanger ringpositionable about an external surface of the casing hanger; and apack-off plate positioning positioned between the shoulder of the casinghanger and a portion of the head ring, the pack-off plate having aninner portion threadably connecting to a third threaded connection onthe external surface of the casing hanger, the pack-off plate having anouter portion sealably engaging an internal surface of the casing head,the pack-off plate comprising a lip positionable in wedged engagementbetween the hanger ring and a portion of the external surface of thecasing hanger.
 38. The assembly of claim 37, wherein the casing head forthe double-bowl arrangement comprises and at least two head componentsinterconnectable to one another, a first of the head components havingthe internal shoulder therein, a second of the head components havingthe first external threaded connection to which the head ring threadablyconnects.
 39. The assembly of claim 37, wherein the casing hangerdefines at least one flute, and wherein the at least one pack-off plateseals fluid communication through the at least one flute.
 40. Theassembly of claim 37, wherein the pack-off plate comprises— a first pairof sealing seats on the outer portion, a second pair of seals sealingseats on the inner portion, and a test port defined in an upper surfaceof the plate and accessible through the opening in the head ring, thetest port communicating with the outer portion between the first pair ofsealing seats and communicating with the inner portion between thesecond pair of sealing seats.